Sharif Digital Repository

Beside the major objective of providing congestion control, achieving predictable queuing delay, maximizing link utilization, and robustness are the main objectives of an active queue management (AQM) controller. This paper proposes an improved queue dynamic model while incorporating the packet drop probability as well. By applying the improved model, a new compensated PID AQM controller is developed for Transmission Control Protocol/Internet Protocol (TCP/IP) networks. The non-minimum phase characteristic caused by Padé approximation of the network delay restricts the direct application of control methods because of the unstable internal dynamics. In this paper, a parameter-varying dynamic... 

In airplanes, engine mounting structures have two primary performances: 1- They sustain all loads which engines produces or those which are exerted on engines in different maneuvering conditions. 2- They make the thrust load and the centric line of its containing cabin concentric [1]. In this paper, analysis of a mounting engine structure with the purpose of the accurate adjustment of the engine in its cabin is presented. Some sample diagrams, which introduced ideal adjustment angles for a specific aircraft, is proposed. These diagrams are obtained with the help of a MATLAB program that can be used for any dimension of the engine and cabin. Therefore, with the aid of these diagrams or this... 

When the network suffers from congestion, the core or edge routers signal the incidence of congestion through the active queue management (AQM) to the sources. The time-varying nature of the network dynamics and the complex process of retuning the current AQM algorithms for different operating points necessitate the development of a new AQM algorithm. Since the non-minimum phase characteristics of the network dynamics restrict direct application of the proportional-integral-derivative (PID) controller, we propose a compensated PID controller based on a new control strategy addressing the phase-lag and restrictions caused by the delay. Based on the unstable internal dynamics caused by the... 

This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien–Tanner (PTT) model with the Gordon–Schowalter convected derivative which covers the upper convected Maxwell, Johnson–Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson–Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid... 

This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien–Tanner (PTT) model with the Gordon–Schowalter convected derivative which covers the upper convected Maxwell, Johnson–Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson–Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid... 

In this paper, a free vibration analysis of moderately thick circular functionally graded (FG) plate integrated with two thin piezoelectric (PZT4) layers is presented based on Mindlin plate theory. The material properties of the FG core plate are assumed to be graded in the thickness direction, while the distribution of electric potential field along the thickness of piezoelectric layers is simulated by sinusoidal function. The differential equations of motion are solved analytically for two boundary conditions of the plate: clamped edge and simply supported edge. The analytical solution is validated by comparing the obtained resonant frequencies with those of an isotropic host plate. The... 

In the eld of supply chain, selecting a suitable green supplier could signi cantly help us decrease the cost and risks of the operations and increase the quality of green supply. This paper develops an integrated two-stage approach based on Fuzzy Analytic Hierarchy Process (FAHP) and multi-objective mixed-integer linear programming to select suppliers and allocate order in the green supply chain. In the rst stage, suppliers are evaluated using FAHP method and in the second stage, a multi-product multi-period supply chain is developed considering green location-routing problem, discounting, and time window under uncertainty. Then, a fuzzy solution approach is applied to solve the proposed... 

Switched Reluctance Motors (SRMs) are widely used in high-speed and low voltage applications because of their attractive features such as robustness and simplicity. No winding on the rotor of this type of motors allows reaching high speed which is desired for many applications. Drive circuits of SRMs also play an important role in their performance and operation. In this paper, a new bifilar drive circuit for this type of motors has been proposed. This novel configuration has been tested and investigated by PSIM software. Results show that the new bifilar drive circuit highly reduces the voltage stresses on semiconductor switches, and also considerably reduces the switching losses which are... 

In this paper, the hydrodynamic performance, cavitation inception, and acoustic performance of a 5-bladed B-series propeller are experimentally investigated in the Sharif University of Technology cavitation tunnel. For hydrodynamic performance, thrust, torque, and efficiency of the propeller model were measured in open water tests. In the cavitation study, in addition to blade cavitation, tip vortex cavitation was also observed, and the cavitation bucket diagram was extracted in different advance coefficients. Finally, for the acoustic analysis of the propeller, the emitted noise in the cavitation tunnel was recorded using two hydrophones according to the recommended procedures of the... 

Background MicroRNAs (miRNAs) are frequently deregulated in various types of cancer. While antisense oligonucleotides are used to block oncomiRs, delivery of tumour-suppressive miRNAs holds great potential as a potent anti-cancer strategy. Here, we aim to determine, and functionally analyse, miRNAs that are lowly expressed in various types of tumour but abundantly expressed in multiple normal tissues. Methods The miRNA sequencing data of 14 cancer types were downloaded from the TCGA dataset. Significant differences in miRNA expression between tumor and normal samples were calculated using limma package (R programming). An adjusted p value < 0.05 was used to compare normal versus tumor miRNA... 

Semantic Textual Relatedness holds significant relevance in Natural Language Processing, finding applications across various domains. Traditionally, approaches to STR have relied on knowledge-based and statistical methods. However, with the emergence of Large Language Models, there has been a paradigm shift, ushering in new methodologies. In this paper, we delve into the investigation of sentence-level STR within Track A (Supervised) by leveraging fine-tuning techniques on the RoBERTa transformer. Our study focuses on assessing the efficacy of this approach across different languages. Notably, our findings indicate promising advancements in STR performance, particularly in Latin languages.... 

Hot isotherm compression tests were performed in temperature range of 350-500 °C and at strain rates of 0.0005 to 0.5 s-1 for Al6061 alloy reinforced with alumina nanoparticles. Effect of deformation parameters and optimal conditions for hot working this nanocomposite were comprehended thoroughly via hot working data analyses, electron microscopy images, and X-ray diffractograms. The results indicated the severity of hot deformation process and an increase in the activation energy to 320 kJ/mol due to the addition of nanoparticles. Dynamic recovery (DRV) was considered as the individual determinative softening mechanism during hot deformation of this nanocomposite, and no sign of dynamic... 

In this article, the flow field around NACA0024 airfoil with step at lower and upper surfaces is experimentally investigated. For this purpose, particle image velocimetry technique based on the instantaneous flow structures is used to investigate the flow field around the airfoil at different times. All the experimental measurements in current study are conducted at very low Reynolds number condition based on the chord of the airfoil (Re=2000) and at angles of attack at 0° and 5° where the flow around airfoils is separated. The differences between vortical structures, mean streamlines, sizes of the wake regions, and vortex shedding of the stepped airfoils compared to unmodified airfoil are... 

STUDY DESIGN. Three factors mixed-design with 1 between-subject and 2 within-subject factors. OBJECTIVE. To compare the main effects and interactions of postural and cognitive difficulty on quiet stance between subjects with and without nonspecific low back pain (LBP). SUMMARY OF BACKGROUND DATA. The interference between postural control and cognitive tasks depends on factors such as sensorimotor/cognitive integrity. Changes in peripheral sensory and muscular systems as well as cognitive processes have been observed in LBP patients. It was hypothesized that the effect of cognitive task on postural performance might be different in subjects with nonspecific LBP as compared with healthy... 

A micromechanical phase-field model is utilized to study the evolution of nanostructure Al3Sc phase in Al-Sc alloy. We study the formation of Al3Sc precipitates in an Al-Sc alloy by using an elastic phase-field model. Since the precipitates of Al3Sc phase are fully coherent with the Al matrix, the elastic energy will have an inuence on the resulting morphology. We have studied the effects of elastic strain energies on shape evolution of Al3Sc phase, numerically. The simulated nano-structures evolve from spherical to cubic shapes. The equilibrium shape of the coherent Al3Sc phase is found to be determined by minimizing the sum of the elastic and interfacial energies through the phase-field... 

In this paper, after studying the demands and requirements of a perfect smart grid and specifications of network topology and sensor nodes utilized in a Wireless Sensor Network [WSN], a manipulated version of them is proposed to be combined with smart grid in order to improve the data acquisition step, increase the security and facilitate the process of information and desired commands from users. We will take the advantage of computer simulations to illustrate improved capacity and speed of this method. Finally, we will analyze the advantages of employing this proposed structure in a smart grid  

This is the first research on the free vibration analysis of functionally graded graphene platelets reinforced composite (FG-GPLRC) viscoelastic annular plate resting on the visco-Pasternak foundation and subjected to the nonlinear temperature gradient and mechanical loading within the framework of higher-order shear deformation theory (HSDT). Hamilton's principle is employed to establish governing equations within the framework of HSDT. In this paper, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Generalized differential quadrature method (GDQM) is applied... 

In this study, a cylindrical microshell stability reinforced by graphene nanoplatelets is investigated while an axial load is applied uniformly. In addition, viscoelastic foundation covers the composite nanostructure. Therefore, the impacts of the small scale parameter are studied while nonlocal strain gradient theory (NSGT) is considered. The present research deals for the first time with the consideration of viscoelastic, strain–stress size-dependent parameters along with taking into account of various boundary conditions (BCs), especially C-F ones put into effect on the proposed theory. The governing equations (G.Eqs) and BCs have been obtained utilizing energy method and solved with... 

In this study, a cylindrical microshell stability reinforced by graphene nanoplatelets is investigated while an axial load is applied uniformly. In addition, viscoelastic foundation covers the composite nanostructure. Therefore, the impacts of the small scale parameter are studied while nonlocal strain gradient theory (NSGT) is considered. The present research deals for the first time with the consideration of viscoelastic, strain–stress size-dependent parameters along with taking into account of various boundary conditions (BCs), especially C-F ones put into effect on the proposed theory. The governing equations (G.Eqs) and BCs have been obtained utilizing energy method and solved with... 

The rare presence of circulating tumor cells (CTCs) in the bloodstream has made their recording and separation one of the major challenges in the recent decade. Inertia-based microfluidic systems have received more attention in CTCs separation due to their feasibility and low cost. In this research, an inertial microfluidic system is proposed using a curved expansion-contraction array (CEA) microchannel to separate CTCs from white blood cells (WBCs). First, the optimal flow rate of the proposed microfluidic device was determined to maximize the separation efficiency of the target cells (CTCs) from the non-target ones (WBCs). Then, the efficiency and purity of the straight and curved-CEA...